Instrument panel radio antenna

ABSTRACT

An instrument panel assembly located beneath the windshield opening of an automobile, including a metal conductor in the form of a metal coating sprayed onto a non-conductive top portion of a rigid insert within the instrument panel assembly for collecting radio waves directly through the windshield opening from outside the vehicle to thereby provide an antenna for a radio receiver.

United States Patent [191 June 11, 1974 Smith INSTRUMENT PANEL RADIOANTENNA Primary Examiner-431i Lieberman [75] Inventor. Stanley E. Smith,Dayton, Ohio Attorney Agent or Firm peter f Kozak [73] Assignee: GeneralMotors Corporation,

Detroit, Mich.

[22] Filed: June 11, 1973 57 ABSTRACT [21] Appl. No.: 368,539

An instrument panel assembly located beneath the windshield opening ofan automobile, including a [52] US. Cl 343/713, 343/873, 180/90, meta]conductor in the form of a metal coating 264/45 264/104 sprayed onto anon-conductive top portion of a rigid Ill. CI. ll0lq insert i i theinstrument panel assembly for COL [58] new of Search 343/711 lectin'gradio waves directly through the windshield 180/90 264/45 104 openingfrom outside the vehicle to thereby provide an antenna for a radioreceiver. [5 6] References Cited FOREIGN PATENTS OR APPLICATIONS Germany343/713 6 Claims, 5 Drawing Figures 1 INSTRUMENT PANEL RADIO ANTENNAFIELD OF INVENTION DESCRIPTION OF PRIOR ART The provision of an idealantenna for an automobile has been a problem virtually since radiosbecame a commonplace feature of the automobile. External antennas suchas the common mast antenna have the obvious advantage of being totallyexposed to the radio waves. They also have obvious disadvantages ofbeing subject to physical damage or loss due to collision with treebranches and the like, chemical deterioration such as corrosion,vandalism and theft. Efforts to deal with these disadvantages haveusually been at considerable expense in the form of chrome platedtelescopic antenna structures, motorized withdrawal devices and thelike.

The design of interior antennas involves a serious problem in that themetal vehicle roof and body functions as an electromagnetic shield whichimpairs proper operation of an antenna located within the automobilebody. A form of interior antenna in successful use today is thewindshield antenna wherein one or more thin conductors are supportedupon or embedded within the windshield of the vehicle. Although thisform of antenna avoids many of the problems associated with the mastantenna, it has been found to have disadvantages in that windshieldwipers may have undesirable effects on the windshield antenna operationincluding the generation of noise andthe precipitation of FM stationswapping. Further, the location of the conductors in the windshield, isrelatively costly and, of course, adds to the cost of Windshields andwindshield replacement.

v SUMMARY OF THE INVENTION It is an object of this invention to providean efficient and economically constructed radio antenna formed as anintegral partof and within the instrument panel pad of an automobilewhich is located under the windshield so that radio waves passingthrough the windshield opening from outside the vehicle irradiate thetop portion of the radio instrument pad and hence the antenna locatedwithin the pad. This antenna construction avoids the disadvantages ofthe outside antenna and also that of the windshield antenna previouslymentioned.

It is a further object of this invention to provide an antenna which ismade incident to the normal method for making the instrument panel padwhereby the cost of making the antenna is minimized.

These and other objects are accomplished by a method including the stepsof providing a rigid electrically non-conductive insert orstructural-frame as is conventional in present day methods for makinginstrument panel assemblies, flame spraying a suitable metal over asuitable pattern on the top side of the insert in a desiredconfiguration to provide a thin adherent metal layer on the insert,providing an electrical connector means for connecting the sprayed metallayer to a radio lead, providing a flexible preformed thermoplasticresin cover layer for the instrument panel'pad and thereafter foaming asynthetic resin between the insert and the skin layer so that a cushionis provided over the insert and the metal layer is embedded within theinstrument panel pad.

BRIEF DESCRIPTION OF THE DRAWINGS Other objects and advantages of theinvention will be apparent from the following detailed description of anembodiment of an invention reference being made to the accompanyingdrawings in which FIG. 1 is a perspective view of a rigid electricallynon-conductive insert for an instrument panel pad with a sheet metalmask positioned thereover having a pattern cut therethrough to exposepredetermined portions of the insert;

FIG. 2 is another perspective view of the instrument panel insert ofFIG. 1 having a metallized layer formed on the said predeterminedportions of the insert;

FIG. 3 is a cross-sectional view of the insert taken along line 3-3 ofFIG. 2 showing the electrical connector;

FIG. 4 is a perspective view of the instrument panel pad of thisinvention with a portion broken away which includes the insert of FIG. 1located in an automobile beneath the windshield thereof, and

FIG. 5 is a cross-sectional view taken along line 55 of FIG. 4 showingthe completed instrument panel pad including the antenna.

DESCRIPTION OF THE PREFERRED EMBODIMENT A typical instrument panelassembly in use on automobiles today which will be hereinafter describedin greater detail, consists of a rigid glass fiber-reinforced syntheticresin insert 10 as shown in FIG. 1 of the drawings which is covered witha suitable decoratively grained synthetic resin skin layer and has asuitable cushion or pad interposed between the insert 10and the skinlayer. The skin layer serves as the top surface of the instrument panelpad which is located directly beneath the windshield opening of theautomobile.

In general, the method of making the instrument panel pad includes thesteps of molding the insert 10 having a top substantially horizontalportion 12 and a depending portion 14 including an opening 16 forreceiving the instrument cluster on the drivers side of the automobile.The insert 10 is usually formed of a glass fiber-reinforced polystyreneor a glass fiber-reinforced styrene-acrylo-nitrile copolymer. A flexiblegrained thermoplastic synthetic resin skin or surface layer is preformedwhich serves as the cover layer or skin of the instrument panelassembly. The skin layer is usually made by a vacuum formingmethod inwhich a sheet of the synthetic resin is heated to its softeningtemperature and then drawn by vacuum over a suitable mold. After coolingthe preformed skin is placed into a female mold cavity which has thesame contours of a preformed skin layer with grained or outer surfacesbeing in contact with the mold surface. The insert is then locatedwithin the mold in a fixed spaced relation to the skin layer. A foamablesynthetic resin mixture such as one leading to the formation ofpolyurethane-foams is injected into the space between the skin layer andthe insert. Usually the mold is preheated to accelerate the foamingreaction. After the resin mixture has reacted fully to fill thespace-between the insert and the skin layer, the resultant instrumentpanel pad is ready for installation in the vehicle body.

This invention involves flame spraying a layer of molten metal insuitable antenna configuration on the top surface 12 of the insert 10. Asuitable electrical connection is provided whereby the sprayed layer maybe electrically connected to a radio antenna lead. Thereafter the insertis associated with the skin and foam layers as above described to formthe pad in the conventional manner.

Referring to FIG. 1, the insert 10 is formed of a rigid electricallynon-conductive material, preferably glass fiber-reinforced polystyreneor a styrene-acrylonitrile copolymer. The antenna is made by firstdegreasing the surface 12 of the insert 10 to insure that the metallayer sprayed thereon adheres firmly thereto. This is accomplished bywashing the surface 12 with a water and soap solution or by subjectingthe surface to the flame of a torch whereby oil or like materials areburned off. Thereafter a sheet metal mask 18 is placed over the insertsurface 12 with the cut-out portion 20 of a desired antennaconfiguration. The mask is formed so that it may be placed withinapproximately 0.05 in. of the insert to assure adequate definition ofthe antenna.

An important feature of this invention is that it permits considerableflexibility in antenna design to obtain optimum performance It isdesirable to provide an antenna with a maximum length-widthconfiguration to maximize the area which is exposed to radio wavebombardment. On the other hand it is necessary to match the capacitanceof the radio with the capacitance of the antenna. This is accomplishedby removing the portions of antenna surface as necessary to achieveproper capacitance balance. In the embodiment shown in the drawings, theantenna is in the form of a series of tingers extending from anelongated bar to provide good.

length-width configuration. The portions between the fingers are suchportions as have been removed to achieve capacitance balance. Further,the antenna is located on the passenger side of the instrument panel padto avoid interference from the instruments. The antenna could be made toextend over the drivers side of the instrument panel pad and hencesubstantially across the entire length of the instrument pad providedthat suitable shielding is provided between the antenna and theinstrument cluster situated in the opening 16.

Next a layer 23 of zinc about 0.002 inch thick is sprayed over thecut-out portion 20 of the shield 18. This is accomplished by means of aflame spraying gun such as the Metco System using an oxyacytelene wiregun. It has been found that two hand passes with this gun spraying zincforms a continuous layer about 2 mils in thickness with excellentadhesion to the synthetic resin substrate.The electrical reistance fromend to end of the antenna was 0.2 ohms. Satisfactory ohmic resistancewith good adhesion to the plastic substrate may be obtained with asprayed metal thickness of from about 0.002 to 0.005 inch. In general itis preferred to use the minimum metal thickness which will provide acoextensive sprayed coating on the insert. Metal thickness in excess of0.005 inch have inferior adhesion. Zinc is preferred as the antennamaterial because its relatively low melting temperature of 790F makesrelatively rapid spraying practical without damage to the plasticinsert, the metal is non-toxic, adheres well to the The shield 18 isthen removed to reveal the antenna 23 shown in FIG. 2 in the form of the2 mil thick layer of zinc. The zinc layer 23 is then electricallyconnected to a connector device 21 shown in FIG. 3 which consists of astud 22 and a mushroom shaped head 24 having yieldable peripheralportions 25 which are yieldably urged into contact with the antenna 23and held in this condition by means of the annular resilient retainer 26which engages the stud 22 in a well known manner. The end of the stud 22is adapted for attachment to the radio lead-in wire. The location of theconnector device is important in that it determines the capacitance ofthe antenna in relation to the capacitance of the radio and lead-inwire. An important advantage of the antenna of this invention is thatthe location of the connector 21 may be varied to meet the electricaldesign requirements. a

The insert 10 is then incorporated into an instrument panel pad assembly28 as above described and as shown in FIGS. 4 and 5. The instrument padassembly 28 accordingly consists of the outer skin layer 30, the saidinsert 10 having the flame sprayed antenna 23 including the electricalconnector 22 and the flexible foam resin 32 which encapsulates theantenna in the instrument panel pad. The pad assembly 28 is locatedbeneath the windshield 34 and the windshield opening so that radio wavespassing through the windshield opening from outside the vehicle mayirradiate the horizontal portion of the pad.

Although zinc (790F MP) is preferred for use as the antenna metal, otherlow melting point metals have been found satisfactory. Using the mask 18of FIG. 1 and a suitably cleaned insert 10, a coextensive tin (450F MP)layer was flame sprayed on the insert in two passes with good adhesion.The ohmic resistance was found to be 0.4 compared to 0.2 for zinc. Alead free babbit (450F MP) layer was applied in a similar experimentwith good adhesion and an ohmic resistance of 1.0. On the other hand ina similar experiment aluminum (1,200F MP) applied .by five passes of thespray gun produced a discontinuous and cracked coating with pooradhesion. Similarly a copper layer applied with ID passes produced acracked and discontinuous layer with poor adhesion. Lead is consideredundesirable because of its toxicity.

As shown in FIGS. 4 and 5 the instrument panel pad is adapted forinsertion directly under the vehicle windshield where the performance ofthe antenna has been found to be equal to or superior to the windshieldantenna.

It is preferred to spray the antenna over the top side of the insert 10because this surface is usually relatively smooth. Applying the coatingto the underside is not preferred because the underside usually hasrecesses which are difficult to spray into and because of the danger ofgrounding the antenna. Further the coating should be located so as to beat least two inches from car body metal.

The term babbit as used in the claims is intended to refer to alloysconsisting essentially of 65 to parts by weight tin, 8 to 12 partsantimony and about 1 part copper.

While the invention has been shown and described in terms of certainembodiments various modifications will be apparent to those skilled inthe art.

It is claimed:

1. A method for making a radio antenna in combination with an instrumentpanel pad for an automobile, said panel pad having a generallyhorizontal portion adapted to underlie radio waves passing through saidwindshield opening from outside the vehicle may irradiate saidhorizontal portion comprising the steps of:

providing a rigid electrically non-conductive insert having a generallyhorizontal portion corresponding to said instrument panel horizontalportion and a preformed decorative electrically nonconductive coverportion for said panel,

masking off a portion of said insert horizontal portion to leave exposedthereon a predetermined elongatedportion along the length thereof,

flame spraying and bonding on said elongated exposed portion acontinuous layer of an electrical conductor metal,

locating said cover portion in a female mold,

locating said insert within said female mold in spaced relation to saidcover portion with said metal layer facing said skin layer,

injecting a foamable synthetic resin composition between said skin layerand said insert and foaming said composition to fill the space betweensaid insert and said cover layer therewith and to encapsulate said metallayer within said instrument panel.

2. A method for making a radio antenna in combinationwith an instrumentpanel pad for an automobile, said panel pad having a generallyhorizontal portion adapted to underlie the windshield opening so thatradio waves passing through said windshield opening from outside thevehicle may irradiate said horizontal portion comprising the steps of:

providing a rigid electrically non-conductive insert having a generallyhorizontal portion corresponding to said instrument panel horizontalportion and a preformed decorative electrically nonconductive coverportion for said panel,

masking off a portion of said insert horizontal portion to leave exposedthereon a predetermined elongated portion along the length thereof,

flame spraying on said exposed elongated portion a metal selected fromthe class consisting of zinc, tin and babbit to provide thereon a metallayer about 0.002 to 0.005 inch thick bonded to said insert, locatingsaid cover portion in a female mold, locating said insert within saidfemale mold in spaced relation to said cover portion with said metallayer facing said skin layer, injecting a foamable synthetic resincomposition bethe windshield opening so that 5 tween said skin layer andsaid insert and foaming said composition to fill the space between saidinsert and said cover layer therewith and to encapsulate said metallayer within said instrument panel.

3. The method of claim 2 wherein said metal is zinc.

4. A radio antenna in combination with an instrument panel for anautomobile, said panel having a generally horizontal portion adapted tounderlie the windshield opening so that the radio waves passing throughsaid windshield opening from outside the vehicle may irradiate saidhorizontal portion comprising:

a rigid electrically non-conductive insert having a generally horizontalportion corresponding to said instrument panel horizontal portion and apreformed decorative electrically non-conductive cover portion,

a continuous elongated flame sprayed electrically conductive metal layerof a predetermined elongated configuration coextensively bonded to saidhorizontal portion,

said insert being disposed in spaced relation to said cover portion withsaid metal layer facing the cover portion and a layer of foamedsynthetic resin interposed between said insert and said cover layer andencapsulating said metal layer within said instrument panel.

5. A radio antenna in combination with an instrument panel for anautomobile, said panel having a generally horizontal portion adapted tounderlie the windshield opening so that the radio waves passing throughsaid windshield opening from outside the vehicle may irradiate saidhorizontal portion comprising:

a rigid electrically non-conductive insert having a generally horizontalportion corresponding to said instrument panel horizontal portion and apreformed decorative electrically non-conductive cover portion,

an elongated flame sprayed metal layer about 0.002 to 0.005 inch thickselected from the class consisting of zinc, tin and babbit of apredetermined elongated configuration coextensively bonded to saidhorizontal portion,

said insert being disposed in spaced relation to said cover portion withsaid metal layer facing the cover portion and a layer of foamedsynthetic resin interposed between said insert and said cover layer andencapsulating said metal layer within said instrument panel.

6. The antenna of claim 5 wherein said metal layer is

1. A method for making a radio antenna in combination with an instrumentpanel pad for an automobile, said panel pad having a generallyhorizontal portion adapted to underlie the windshield opening so thatradio waves passing through said windshield opening from outside thevehicle may irradiate said horizontal portion comprising the steps of:providing a rigid electrically non-conductive insert having a generallyhorizontal portion corresponding to said instrument panel horizontalportion and a preformed decorative electrically non-conductive coverportion for said panel, masking off a portion of said insert horizontalportion to leave exposed thereon a predetermined elongated portion alongthe length thereof, flame spraying and bonding on said elongated exposedportion a continuous layer of an electrical conductor metal, locatingsaid cover portion in a female mold, locating said insert within saidfemale mold in spaced relation to said cover portion with said metallayer facing said skin layer, injecting a foamable synthetic resincomposition between said skin layer and said insert and foaming saidcomposition to fill the space between said insert and said cover layertherewith and to encapsulate said metal layer within said instrumentpanel.
 2. A method for making a radio antenna in combination with aninstrument panel pad for an automobile, said panel pad having agenerally horizontal portion adapted to underlie the windshield openingso that radio waves passing through said windshield opening from outsidethe vehicle may irradiate said horizontal portion comprising the stepsof: providing a rigid electrically non-conductive insert having agenerally horizontal portion corresponding to said instrument panelhorizontal portion and a preformed decorative electricallynon-conductive cover portion for said panel, maskIng off a portion ofsaid insert horizontal portion to leave exposed thereon a predeterminedelongated portion along the length thereof, flame spraying on saidexposed elongated portion a metal selected from the class consisting ofzinc, tin and babbit to provide thereon a metal layer about 0.002 to0.005 inch thick bonded to said insert, locating said cover portion in afemale mold, locating said insert within said female mold in spacedrelation to said cover portion with said metal layer facing said skinlayer, injecting a foamable synthetic resin composition between saidskin layer and said insert and foaming said composition to fill thespace between said insert and said cover layer therewith and toencapsulate said metal layer within said instrument panel.
 3. The methodof claim 2 wherein said metal is zinc.
 4. A radio antenna in combinationwith an instrument panel for an automobile, said panel having agenerally horizontal portion adapted to underlie the windshield openingso that the radio waves passing through said windshield opening fromoutside the vehicle may irradiate said horizontal portion comprising: arigid electrically non-conductive insert having a generally horizontalportion corresponding to said instrument panel horizontal portion and apreformed decorative electrically non-conductive cover portion, acontinuous elongated flame sprayed electrically conductive metal layerof a predetermined elongated configuration coextensively bonded to saidhorizontal portion, said insert being disposed in spaced relation tosaid cover portion with said metal layer facing the cover portion and alayer of foamed synthetic resin interposed between said insert and saidcover layer and encapsulating said metal layer within said instrumentpanel.
 5. A radio antenna in combination with an instrument panel for anautomobile, said panel having a generally horizontal portion adapted tounderlie the windshield opening so that the radio waves passing throughsaid windshield opening from outside the vehicle may irradiate saidhorizontal portion comprising: a rigid electrically non-conductiveinsert having a generally horizontal portion corresponding to saidinstrument panel horizontal portion and a preformed decorativeelectrically non-conductive cover portion, an elongated flame sprayedmetal layer about 0.002 to 0.005 inch thick selected from the classconsisting of zinc, tin and babbit of a predetermined elongatedconfiguration coextensively bonded to said horizontal portion, saidinsert being disposed in spaced relation to said cover portion with saidmetal layer facing the cover portion and a layer of foamed syntheticresin interposed between said insert and said cover layer andencapsulating said metal layer within said instrument panel.
 6. Theantenna of claim 5 wherein said metal layer is zinc.